The present invention relates to polyene compounds and more particularly to arylnonatetraenoic acids and derivatives derived from intermediates represented by the general formula: ##STR3## where R.sub.1 is H or lower alkyl of from 1 to 5 carbon atoms; R is H, lower alkyl of from 1 to 8 carbon atoms or aralkyl and n is from 0 to 3. A synthesis of 2,3,6-trimethyl-p-anisaldehyde is described in U.S. Pat. No. 4,105,681. The same patent also describes compounds of the formula: ##STR4## wherein R is formyl, hydroxymethylene, alkoxymethylene, alkanoyloxymethylene, carboxyl, alkoxycarbonyl, alkenyloxycarbonyl, alkynyloxycarbonyl, carbamoyl, mono(lower alkyl)-carbamoyl, di(lower alkyl)-carbamoyl, or N-heterocyclylcarbonyl; and pharmaceutically acceptable salts thereof useful as anti-tumor agents.
A synthesis of 5-(4-methoxy-2,3,6-trimethylphenyl)-3-methyl-2,4-pentadien-1-al is described in U.S. Pat. No. 4,137,246 and Swiss Patnet No. 616,134. A synthesis of 5-(2,3-dimethyl-4-methoxyphenyl)-3-methyl-2,4-pentadien-1-al is described in U.S. Pat. No. 4,534,979. M. P. Reddy, et al. (Synthesis, 1980,(10),815-18) describes the synthesis of certain 5-aryl-3-methyl-2(E),4(E)-pentadienals.